Automatic station control



Jan. 13, 193L A. J. A. PETERSON AUTOMATIC STATTON CONTROL Filed May 27,.1929 2 sheeisvsheef, 1

Lu T D maf/ INVENTOR AlFIed JAPeifnSfoTl ATTORN EY `lan. 13, 1931. A. J.A. PETERSON AUTOMATIC STATION CONTROL Filed May 27 1929 2 Sheets-Sheet 2INVENTOR Alfr ed J: APetefsCm ATTORNEY Patented Jan. 13, 1931 UNITEDSTATES PATENT OFFICE ALFRED J. A. PETERSON, OF WILKINSBURG,PENNSYLVANIA, ASSIGNOR TO` WESTING- HOUSE ELECTRIC & MANUFACTURINGCOMPANY, A CORPORATION F PENNSYL- VANIA AUTOMATIC STATION CONTROLApplication filed May 27, 1929. Serial No. 366,263.

T his invention rela-tes to automatic stations and, in particular, toautomatic stations including a plurality of translating devices, such astransformers, motor-generators, converters or the like. In automaticstations of this type, it is desirable that sufli lent translatingcapacity shall be connected in circuit to supply the load on the stationand it is equally desirable that, When the station load decreases, anyunneeded translating apparatus shall be disconnected.

It is the principal obj ect of this invention to improve upon thesystems for operating multi-unit stations shown in the Moss Patent No.1,564,303, the Field and Ross application, Serial No. 199,172 filed June16, 1927, and the Moss and Peterson application, Serial No. 287,758,filed .lune 23, 1928.

A specific object of this invention is to provide improved means forcomparing'the station load and the number of the connected translatingdevices.

Another object of my invention is to provide load-measuring means whichshall not be aii'ected by changes in the voltage of the usual auxiliarysupply source.

A further object of my invention is to provide means for varying theorder in Which the several units of a multi-unit automatic station areconnected in service.

In accordance with my invention, I make use of a plurality of standardover-current relays which are adapted to be energized in accordance withthe station load. These relays are set to operate at different values ofstation-load current 'and serve to initiate the operation of connecting`an additional translrating unit in service when the station loadincreases, and to disconnect surplus translating units when the stationload decreases.

For a complete understanding of my invention, reference should be had tothe accompanying drawings in which: i

Figures 1 and 2 illustrate diagrammatically a multi-unit automaticstation embodying the novel features of my invention.

Fig. 3 illustrates, diagrammatically, an element necessary in connectionwith the system shown. in Figs. 1 and 2.

Referring particularly to Figs. land 2, a

high-voltage supply circuit is adapted to supply energy to a relativelylow-voltage load circuit 26 through translating devices, such astransformers 27 28 and 29.

The connection of the transformer 27 between the circuits 25 and 26 iscontrolled by suitable circuit breakers 3() andi 31, in a manner whichwill become apparent hereinafter. It is to be understood at this pointthat, although I have illustrated my invention in connection with atransformer station, any other translating devices, such as rotaryconverters, motor-generators, vapor converters, or the. like may becontrolled by meanssimilar to that shown and described herein. It ispossible, furthermore, to control nonelectrical processes by the somemeans. A

As hereinbefore indicated, the operation of the system of my inventionis initiated inresponse to an increase in the load on the station inwhich the transformers 27, 28 and 29 are located. The stationload ismeasured by the current transformers 32, 33 and 34 connected incorresponding leads of the transformers, in

connection With standard over-current relays 35, 36 and 36. Although Ihave illustrated my invention in connection with a single- .phasesystem, it is obvious thatl it may be applied to any polyphase system.In such case, a relay corresponding to relays and 36 Will be providedfor each phase, and the front and back contacts thereof will beconnected in parallel and in series, respectively, as taught by theVEdmonds Patent No.l 1,67 5,336.

The remaining equipment necessary in the embodiment of my inventionhereiny shown will be described in the course of the followingexplanation of the operation thereof.

It is desirable, in multi-unit automatic stations, that at least onetranslating device shall be connected between the supply and loadcircuits at all times. In order to insure this condition, I provide abalance relay37. This relay is arranged to control the operationsrequired to connect an additional translating device between saidcircuits under the influy windings of the relay are deenergized, as whenthe apparatus is in the condition illustrated in Figs. 1 and 2, theContact 38 ot the relay will be closed to complete a circuit from asource of auxiliary control current, such as the automatic bus 39,through the relay arm and the contacts 38. to the winding of an auX-iliary relay and the negative side of the control circuit (representedby a minus sign within a circle). Current is supplied to the automaticbus from any convenient source, as will be explained more fully later.Instead of biasing spring, one of the windings of the relay 37 may bepermanently energized, in series with a resistor of appropriate value,to exert a biasing torque on the contact lever of the relay.

The relay 40, when energized, closes its contacts 41, 42 and 43. Theclosing of the contact 42 of the relay 40 completes a circuit from theautomatic bus 39, through a normally closed contact 44 of a masterlockout relay 45, the operation of which will be described furtherhereinafter, the contact 42 of the relay 40 and the armature 46 of areversible motor 47, to the negative bus. A circuit is likewisecompleted at the contact 43 ot the relay 40 for the forwardlield'winding 48 of motor `47.

The motor 47 serves to drive a drum switch 49 comprising conductingsegments 50 to 56, inclusive, which are adapted to f cooperate withcontact lingers 58 to 64, inclusive. When the motor 47 is energized bythe completion of the circuits hereinbetore mentioned, the motor startsto rotate in such direction as to cause the contact segments 50 to 56 toengage the lingers 58 to 64. Appropriate gearinginay Y be interposedbetween the motor 47 and the drum 49 to reduce the speed of the latter.By the operation of the relay 40, a circuit is also completed from theautomatic bus39, through the Contact 41 of the relay 40, conductor 58 tothe corresponding contacts of a plurality of sequence switches 67, 68and 69, which determine theorder in whichv the transformers 27, 28 and29 are connected between the circuits 25 and 26. An extension of theconductor 58 is connected to the contact finger 58 for a purpose toappear subsequently. f

The sequence switch 67 is shown in detail in Fig. 3 and consists et amanually operable drum 70, preferably cylindrical, bearing segments 71to 76, inclusive, which areV adapted to engage stationary contactlingers 81 to 88, and 92 when the drum isrotated through its variouspositions A, l5, C and D. A pointer 93 indicates to the operatontheposition of the Contact segments with respect to the contact lingers,and any suitable means (not shown may be provided for rotating the drum70 past the Contact lingers 81 to 88, 90 and 92 which are fixed to thestationary portion of the switch structure.

elVhen a sequence switch is` actuatedto po sition A, the translatingdevice associated function of which will be described therewith will bethe lirst te be connected to the supply and load circuits. The unithaving its sequence switch in position B will be connected second in thesequence, and so on. The disconnection of the units will be eected inthe reverse order ot their connection, will be described hereinafter.

Assuming that the sequence switch 67 is in position A, the contactlingers 82 and 84 there et will be connected through the segments 71 and72 in engagement with said lingers, respectively. This being the case,the circuit to the conductor 58 is extended through the Contact fingers84 and 82 of the sequence switch 67, a current-limiting resistor 95 tothe winding of a closing relay 95 associated with the circuit breaker 30and through an auxiliary switch 96 on said breaker, a switch 97, theposition of which is controlled by the manual closing and trippingswitches`98 and 99 in such manner that the switch 97 wi l norinally beclosed untilithe manual-tripping switch 99 is actuated. rlhe circuitextends to the negative bus through the normally closed contact 100 of aunit lockout relay 101, the

rWhen the relay 95 is energized by tne coinpletion of the circuit whichis traced above, it Ycloses its contacts 102 and 103. The closing of thecontact 102 completes a locking circuit for the relay95 in parallel withthe auX- iliary switch 96. The contact 103 completes a circuit fortheclosing coil ot the circuit breaker 30, which is thereupon actuated toits closed position, the source of current 'for the closing coil beingindicated by a plus sign within small circle. rlhe consequent openingoi' the switch 96 does not affect the relay 95 but the closing otanother auxiliary sw 104 on the circuit breaker' 30 completes a circuitrom contact 82 of the sequence switch 67 which is connected to theautomatic bus, through the drum switch 49, as already described, to thewinding ot a cut-cti relay 105. This circuit returns to the negative busin the saine manner as that described 'for the relay 95. The relay 105closes its contacts 106 and 107, the former completing a locking circuitfor the relay 105 in parallel with its original energizing circuit, andthe latter ser g to shunt the winding of the relay 95, which isthereupon deenergized. The relay 1.05 remains energized so long aspositive battery is supplied to kconductor 58. "When relay 40 isdeenergized, however, as will be p ted out later, relay 105 is likewisedeenergized but the circuit breaker 30 remains latched in the closedposition.

`The circuit breaker 30 is provided with auxiliary contacts 108 and 109which are closed when the circuit breaker is closed. The closing Yof theContact 108 extends the circuit previously traced to the contact linger82, through said contact 108V and a currentliiniting resistor 110', tothe winding ci a Cil closingrelay 110 associated Withthe circuit breaker31. This circuit returns to the negative bus through the auxiliaryswitch 111 of the circuit breaker-31, manual.v switch 97 and thelock-outcontact 100. The relay 110 is thereby energizedto close its contacts`112 `and 113. The contact 112 closes a locking circuit for the relay110 in parallel With thatv including the auxiliary switch 111. The.contact 113 closes an energizing circuit for the clos ing coil of thecircuitbreaker 31 which is thereupon actuated to. its closed position;The closing of the circuit breaker 31- Ldoes not allectkthe relay 110sincethecontact 112 of the latter completes a locking circuit there;for, as described above, but the auxiliary switch 114 of thecircuitbreaker 31 completes anenergizing circuit from thecontact linger 82ofthe sequence switch 67, through theauxiliary contact 108 of thecircuit breaker 3() and the resistor 110', tothe Winding ofracutoilrelay 115 and the negative Vbus through the auxiliary contact 114. Therelay 115 is thus energizedto close its contacts 116 and 117. Thecontact 116 shuntsl the Winding of the closing relay 110, and thecontact 117 locks the relay 1l5-in its energized position, so long aspositive batteryV is connected to contact 82 through contact 41ofi'relay 40.

The circuit vbreakers 30..and 31 are now closed, andthe highvoltagecircuit 25 sup.- plies energy to the low-voltage circuit v26 through the.transformer 27. The .highfvoltT age circuit breaker 31, obviously, .maybe closed first instead of the low-voltage breaker 30, ifV desired. Thecircuit breakers are latclied in their closed positions vby latches 118and 119. These latches .are adapted to be Withdrawn by the trippingcoils 120 and 121. The closing of the circuit breakers 30 and 31 alsocompletes one of a plurality of parallel circuits from the automatic bus39, through the Winding. 122 of the relay 37, to a .balancing7 bus 123,through the auxiliary contacts 124 and` 125 of the circuit breakers 31and 30, to a resistor andthe negative bus'. Upon theycompetion of thiscircuit, the coil 122 of the relay 37 is energized,.the latter isthereby restored to balance, andthe circuit for the relay 40 isinterrupted, so that further rota-tion of the motor 47 and the drumswitch 49 is precluded, leaving the segment 50-in engagement With thefinger 5.8 for the time being.

` Conditions in the substation remainunchanged so long as the stationloadremains constant. kUpon an increase. in. the station load, however,to a predeterminedvaluathe relay 35Will operate by reasonV of'theincreased load current supplied by the station, to complete'acircuit, at its Contact 126, for a relay 127. The relay 127voperates andis latched in the operated position by the latch 128. The relay 127,through its contact 129, completes. a circuitfrom the-automatic bus 39;lthroughthe winding130 of the relay 37 andthecontact 129 ofthe relay 127,to .a resistor and ;the negative bus. When the winding 130 of the relay37 isthus'e'nergized,

the torque produced thereby count-erbalances l that exerted by coil 122,andthe-.contacts'38 areagain closedv by the biasing spring, with thesame results as before. `The relay 40 is energizedto start the motor47,*and the drum switch. 49 is again rotated.

When the s egment,51I of the drum switch engages its associatedr contactlingery 59, a circuit iscompleted from the automatic bus 39, through theContact 41 of vthe, relay 40, the contact finger 58, segments 5() and 51and finger 59 of the drum switch49, to the finger 86 of the sequenceswitches 67, 68and 6 9. If it be assumedv that the sequence switch 68occupies the position B, as indicatedl in Fi 3, the fingers` 82 and86thereof will be bridged by the segments 71 and 73,v with theresultthat current is supplied from the automatic bus to the closingrelay (not shown) for the ,circuit Vbreaker 131, which corresponds tothe.V relay 95 shown. in connection WiththeA circuit` breaker 3Q- Thenecessary, controlv` circuits for the circuit breakers associated withthe transformer 28 are not shown in detail. since they. are duplicatesof those shown` in connecton `with circuit `breakers 30 and 31. YAsdescrihed in connectionwith thelatter, the closing of .the circuitbreakers 131 and 132 completes a parallel. circuit from` the balancingbusk 123 to a4 resistor and-thenegative bus so that thecoil 122 of therelay 37 is morestrongly energized than before. The result of thisoperation is torestore the balance of the relay 37, fdeenergize relay 40and stop .the motor 47.

It is obvious that` another..translatingunin such as the transformer 29,may. be connected to the .load and supply. circuitsthrough suitablecircuit breakers 133l and 134, hy. the re` lay 36, which is set tooperate at a higher value,of load current than the relay `35, and the.contact segments52 on the drum switch 4 9 similar to the segment 51.Thesequenceswitchl 69 'may be atl its C position toconnect its fingers81- and 82through segments.. 72 andy 71, whereby the unit 29 is causedto take third place in the operation sequence. v

Alftery all available translating units have beenconnected inservice, itis desirablethat afurther increase in` load be indicated to anattendant.- I, make provision-for such indication in the followingmanner. If allthe transformers 27, 28 and 29 have been connected; inthemanner hereinbefore described, and a further increase in the stationloa-d. occurs. the resulting operation of a relay 36', which is set atthe maximum permissible load, will causethe drum switch 49 .to be:actuated again, asfexplained above.

When the segment 53 engages the finger 61, however, a circuit will becompleted for the master lockout relay 45. The relay 45 operates, and islatched in itsoperated position by a latch 133. At the contact 134 ofthe relay 45, the circuit from positive battery through the manualswitch 135, the contact`r134 to the automatic bus 39 is interrupted, andall devices drawing current therefrom are deenergized. The drivingcircuit for the motor 47 is interrupted at the contact 44 of the relay45 and, at contact 136, a circuit is closed for an'alarm, such as thegong 137. rlhis indicates to an attendant that the station is overloadedand that steps should be taken to reduce the load. rlhe signal device137 may be located in the station if there are attendants present or itmay be placed in any suitable position, such as the oflice of the systemVoperator, which may be located at a considerable distance from thestation. A Y

Afterthe operation of the master lockout relay 45, it is necessary thatan attendant visit the station to reset the lock-out relay bywithdrawing the manual latch 133. Until this is done, all automaticoperation of the station is, of course, suspended, the translating unitsremaining connected, so that no interruption in service occurs.Obviously, the relay 36 may control t-he relay 45 directly instead ofthrough the medium of the drum switch, as shown. The time required forthe operation of the latter, however, prevents the operation of themaster lockout relay 45 upon the occurrence of a temporary overload onthe station.

t will be understood from" statements above made that the current relaysV35, 36

and 36 are set to operate at different values of current so that theyoperate'successively, as the station load increases, to cause the secondand third'units to be connected and the station to be finally locked out'as described hereinabove.k

Assuming` now that the station load has increased to such value that thetransformvers 27 28 and 29 are connected in service but the masterVlockout relay is not operated, if the station load decreases, the relay364 .will be so actuated that its back contact will be closed toenergize the tripping coil 139 of the relay 138. The latter is thereuponreset and the balance relay 37 operates, because of the opening of oneof the plurality of circuits for the left-hand coil thereof at thecontact'129 of the relay 138, tov closeits right-hand contacts 140. Thisresult follows because, after the opening of lcontact 129', theY coil122 is energized more strongly than the coil 130.

The closing of the right-hand contacts of therelay37 completes anobvicusfenergizing circuit for a Arelay 141 which,inr turn, completes acircuit from .the automatic bus 39 through the contact 44 of the relay45 which, itwas assumed, has been reset manually after locking out, aspreviously described, a contact 142 of the relay 141 to the armature 46of the motor 47 L The reverse field winding 143 of the motor issimultaneously energized by the closing of contact 144. rlhe contact ofrelay 141 sets up a circuit froml the automatic bus 39 to the contactiinger 62 of the drum relay 49.

Since it was assumed that the units 27, 23 and 29, were in service, itis obvious that the drum switch 49 will be so positioned that segment 52engages the finger 60. Such be* ing the case nothing will happen untilthe reverse movementof the drum switch causes segment 56 to engagefinger' 64, whereupon the circuit to the linger 62 will be extended,through segments 54 and 56, to a tripping conductor 146 which isconnected to a finger 35 of the sequence switches 67, 63 and 69. lt willbe assumed that the sequence switches 67, 63 and 69 are so adjusted, asbefore stated, that transformer 27 is the lead-o5 unit, and transformers28 and 29 thesecond and third units. tion, the sequence 'switch 67should be placed in position A, sequence switch 63 in position B Vandswitch 69 in position C. The circuit traced to the conductor 146 andcontact finV gers 35 of the sequence switches, therefore, extends fromlinger 35of thesequence switch 69 to segment 74,'segment 76 and finger'92 of said sequence switch.

Since the complete closing and tripping` circuits for the circuitsbreakers 131-134 have not been shown, the tripping of the circuitbreakers 133 and 134 will be described in connection with circuitbreakers 30 and 31, it being remembered that circuit breakers 133 and134are tripped by thel first decrease in the station load sufficient tocause the relay 36 to close its back contact. From the finger 92, thecircuit extends to the tripping coils for the circuit'breakers 133 and134 corresponding to those illustrated'at 120 and 121 for the circuitbreakers 30 and 31. rEhe tripping coils withdraw the latches whichmaintain the circuit breakers closed, and the breakers are tripped inthe usual manner. f

The tripping` of the circuit breakers 133 and 134, at the auxiliarycontacts thereof, opens one of the parallel circuits to the balancingbus 123. IThe lenergization of the coil 122 of the relay 37 is therebyd1 ninished,

To arrange this4 sequence of operaf and the relay 37 is restored'tobalance. The

opening of the contactsV 146Y Vthereof Kile-V energizes the relay 141and stops the motor 7. i

l desire to emphasize, at'this'point, the advantage resulting from thestaggering of the segments 55 and 56 with respect to segments 51and 52.rlhis arrangement of contact segments requires that a movement of theswitch 49 be effected before anyk unit is tripped, and thus introducesa'slight time delay between the decrease in the station load and thereduction in the member of translating units connected. If this timedelay were not. provided, a rapidly fluctuating load on the stationmight cause repeated closing and tripping ofthe circuit breakers 133 and134. This repetition of needless operations is avoided by properlystaggering the contact segments 51, 52 and 55, 56 so that no change inthe number of connected translating devices will be eil'eeted until asubstantial change in load conditions occurs, of sufficient duration topermit the required movement of the switch 49.

Further decrease in the station load will cause the relay 35 kto `closeits back contact to repeat the tripping impulse through the relays 127and 37. Segment 55 of the switch 49 subsequently engages finger 63 toextend a tripping circuit for the circuit breakers 131 and 132 throughlingers 90 and 92 bridged by segments and 76 of sequence switch 68 whichis in position B. The translating units are thus disconnected from theload and supply circuits until the station load is balanced, with thecapacity of the translating devices connected in circuit, or until onlyone unitremains in service.

In addition to the automatic operation described hereinbefore, I providemanual means for controlling the operation ofthe circuit breakers whichconnect the translating units between their load and supply circuits.Examples of these means are the closing and tripping switchesillustrated at 98 and 99. The manual switch 98 is adapted to complete acircuit :for relay 95 from the non-automatic bus 147, which may beconnected to the auxiliary source of current by actuating the manualswitch 135 to the non-automatic position. As a result of the operationof the relay 95, the circuit breakers are closed, as described above.The manual switch 99 is for the purpose of tripping the circuit breakers30 and 31 and, when operated, completes an energizing circuit for thetrip coils 120 and 121.

A partcular feature ofthe manual switch .is that, when the trippingswitch 99 is actuated, the normally-closed back contact97 associatedtherewith is opened and latched to prevent functioning of the automaticcircuit-breaker-controlv equipment. `The latch is released when themanual closing switch 98 is actuated. This feature provides for asuspension of the automatic operation during a period of manualoperation which may be necessary for any reason. Duplicates of themanual switches 98 and 99'will, obviously, also be provided for each ofthe units 28 and 29. An alternative means for manually closing thevarious circuit breakers for connecting the translating units 27, 28 and29 in service is afforded by the connection of the 'automatic bus 39 tocontact fingers 83 ofthe sequence switches 67, 68 and 69. Thus, when thesequence switches are shifted to the D position, in which fingers 82 and83 are engaged by segments 71 and 73, current is supplied to the relayscorresponding to for closing the circuit breakers. This manualoperation, obviously, maybe effected even when the switch'135 is in theautomatic position. The tripping of the breakers might be similarlyaccomplished should this bel desirable but, of courseboth closingandftripping by the sequence switches could not be controlled except byadding other contacts to the sequence switches.

The unit llockout relay 101 may be controlled by any number of suitableprotective devices each of which is adapted to control contacts, such asthose shown at 148. `These contacts are connected in parallel and serveto energize the lockout relay upon the occurrence of any `conditionwhich it is desired to guard against, such as excess load on any unit,excess temperature thereof, or the like. Although only a single lockoutrelay is illustrated, it is desirable that one such relay be providedfor each unit in the station. When any one of the contacts 148 isclosed, the circuit for the relay 101 is completed and its f operationcloses a circuit at contact 149 for the tripping coils 120 and 121 ofthe circuit breakers 30 and 31. The unit lockout relay, furthermore, byopening the automatic control circuit at contact 100, prevents continuedoperation of the transformer 27 in the automatic sequence. Upon theoccurrence of such condition, the balance relay 37 is so actuated as tocause another unit, if available, -to be substituted for thatdisconnected by the protective equipment. The relay 101 is of themanually reset, latching type.

A push-button switch 150 or its equivalent is provided to enable anattendant to reset the motor relay ll7-49 when the station has beenlocked out automatically. As above stated, after a station lockout, itis necessary for an attendant to reset the lockout relay 45. It is alsonecessary for the motorrelay l17-49 to be reset and this is accomplishedby actuating the switch 150 which completes a circuit for the reversewinding of the motor 47. Vhen the relay 47-49 has been reset, the relay37 operates automatically, as described above, to connect the first unitin service and additional units are required.

It will be apparent that the system of my invention provides meanswhereby the aggregate connected translatingcapacity-of an automaticstation may be made to correspond to the station load. This systemobviates certain diliculties experienced in similar systems knownheretofore. vThe principal of these ris that, in the present case, theloadindicating relays respond lonly at a definite value of station load.Exact balancing of the load-indicating relay, therefore, is easilypossible, whereas, in previous systems, the load-indicating coil of thebalance relay was continually subject to changes in its energizetion, inaccordance with stationload, so that maintenance of an exact balance otthe relay was exceedingly diilicult. In this system also, I am able tovary the sequence in which the units are connected by a simpleadjustment of the sequence switch. Upon the lockout of any unit,furthermore, another unit is automatically substituted. .Excesstranslating capacity, also, is automatically disconnected as soon as thestation load decreases to a predetermined value. i

Various changes, modiiications, substitutions, additions and omissionsmay be made in the apparatus illustrated without departing from thespirit and scope of my invention as set forth in the appended claims.

I claim as my invention:

l. An automatic station comprising a plurality of transformers, circuitbreakers for connecting the windings ot said transformers to load andsupply circuits, closing and tripping means for said circuit-breakers, adrum switch adapted to successively energize said closing means whenrotated in one `direction and said tripping moans when rotated in theother direction, a motor for driving said switch in both directions, anda balanced relay for controlling said motor, said rela-y having opposingwindings, one of which is energized in proportion to the numbery ofconnected translating devices, and the other of which is energized by aplurality of over-current relays responsive to successively increasingvalues of the current in the supply circuit and relays controlled bysaid balance relay for causing either the closing or the tripping meansto be energized by said drum switch. y

2. The combination with a plurality oi translating devices,circuit-breakers for connecting said devices to load and supplycircuits, closing and tripping coils for said circuit breakers, of acontroller load-responsiverelay means for energizing said closing coilswhen operated in one direction and said tripping coils when operated inthe reverse direction, means for operating said controller in bothdirections, a relay for controlling said operatine' means, said relayhaving two opposing windings, one controlled by auxiliary switches onsaid circuit-breakers and the other controlled by over-current relaysresponsive to successively increasing values of current in said supplycircuit.

3. ln a multi-unit automatic translating station, a plurality oftranslating' devices, switches for connecting said devices to load andsupply circuits, operating and releasing means for said switches, acontroller for successively energizing said'means, a motor for drivingsaid controller and a two-winding differential relay Jfor controllingsaid motor, auxiliary contacts on said switches for controlling theenergization or" one winding of said relay, and a plurality of relaysresponsive to the current in said supply circuit for controlling theenergization or' the other winding of said ditterential relay.

l. An automatic station comprising a plurality of translating units,means for connecting said units between load and supply circuits, andmeans for successively operating said connecting means, including abalance relay normally biased to effect the connection of one of saidunits between `said circuits, means controlled by said connecting meansfor restoring said relay to neutral, and a plurality of over-currentrelays responsive to predetermined different values of current in saidsupply circuit ror again biasing said balance relay to effect theconnection of an additional unit when the station load exceeds thecapacity of the unit previously connected.

5. An automatic. station comprising a plurality of translatingunits,means Jfor connecting said units to a supply circuit and to a loadcircuit, and means for successively operating said connecting means,including a balancerelay effective in one position to causethesuccessive closing of said connecting means to connect said units tosaid load and supply circuits, and in the other position to cause thesuccessive opening of said connecting means to disconnect said units,means normally biasing said relay to said first-mentioned position, asolenoid controlled by a plurality of relays responsive to the stationload for assisting said biasing means and a solenoid controlled by saidconnecting means for opposing said biasing means, whereby an additionalunit is connected `between said circuits whenever the station loadexceeds a certain relation to 'the number of connected units, and a unitis disconnected whenever the station load has a certainother relation tothe capacity ci the connected units by a predetermined a iount.

6. ln a multi-unit automatic station, supply and load circuits, aplurality of translating units, means for successively connecting saidunits therebetween and disconnecting said units therefromV inthe reverseorder of their connection, a relay for controlling said means and aplurality of over-current relays responsive to different predeterminedvalues of current in said supply circuit for controlling` saidfirst-mentioned relay.

7. In an automatic station, a plurality of translating devices, meansyfor connecting them between load and supply circuits for transferringenergy therebetween, load relays responsive to the total station load, abalance relay having two opposing windings, means whereby said loadrelays control the energization of one of said windings, meanscontrolled by said balance relay for controlling the operation of saidconnecting means and means for controlling the energization of the otherwinding of said balance relay in response to said operation.

8. In an automatic station having a plurality of translating unitsandvmeans including a motor-operated switch for connecting them to loadand supply circuits, a balance `relay for controlling the operation ofsaid connecting means, said relay having opposing windings adapted to beenergized from a common source, and means responsive to the station load,and to the number of said units connected to said circuitsrespectively, for controlling the energization of said windings.

9. An automatic station including a plurality of translating devices,means includin a balance relay responsive to the station loa and thenumber of translating devices in service for varying the number of saiddevices in service, and means for delaying the initiation of theoperation of said devices for a predetermined time after the occurrenceof a predetermined change in the station load comprising a drum switchhaving spaced contacts, adapted to be controlled by said loadresponsivemeans.

l0. In an automatic station, apparatus units, means for rendering saidunits elfective including a balance relay adapted to be controlled inaccordance with the station load and the number of said units connectedin f service, means for biasing said balance relay to maintain at leastone of said units in service at all times, and means including amotoroperated timing device controlled by said re lay for causing otherunits to become effective after a time delay, upon an increase in thestation load.

11. In an automatic station, apparatus units, means for renderingsaidunits effective including a balance relay adapted to be energized from acommon source and controlled in accordance with the station load and thenumber of said units connected in service, and means for biasing saidrelay to maintain at least one of said units in service at all times.

l2. In a control system for a plurality of apparatus units adapted tosupply a common load, means for eifecting the initiation and cessationof the operation of said units, a balance relay having opposingelectro-magnetic operating means for controlling said iirst-mentionedmeans, and means for controlling the energization of said operatingmeans from a single energy source in accordance with the common load andthe number of units connected whereby the effects of Vation of saiddevices, and control means comprising a balance relay for saidfirst-mentioned means responsive only to definite, predetermined changesin the station load.

In testimony whereof, I have hereunto subscribedmy name this 20th day ofMay-1929. 70

ALFRED J. A. PETERSON.

